Animals are multi-cellular, eukaryotic heterotrophs
- Must ingest organic materials
- consume, breakdown internally with enzymes
- Lack structural support from cell walls
- extracellular proteins connect and strengthen cells
- most abundant are collagen (not found in plants/fungi)
- Cells organized into tissues
- similar cells acting as a functional unit
- muscle & nervous tissue allows animals to move
-
Body plan = programmed development driven by evolution

Body plans are coordinated to optimize biological function

Embryonic development key for animal diversity

- Fertilized zygote undergoes
cleavage
- mitotic cell divisions without cell growth
- rapid division but overall size stays same
- protostome vs deuterostome = alignment of cells
- Early multicellular stage called a
blastula (hollow ball)
- Germ (tissue) layers develop in next stage
(gastrulation)
- eventually develop into body parts
- Many animals have larval and adult stage
- larva are sexually immature
- larva look, live and eat differently

Devlopment of the blastopore in different animal groups

-
Blastopore: opening of central cavity of an embryo
- In most animals a second opening forms at opposite end
- become openings of digestive tube
-
Diploblasts: opening to gastrovascular cavity
- Protostomes: blastopore becomes mouth
-
Deuterostomes: blastopore becomes anus
Germ layers (primary cell layers in development)
- Sponges (0), Diploblasts (2), Triploblasts (3)
- germ layers develop into tissues and organs


Body Cavities in Triploblasts
- Fluid/air spaces between mesoderm layers
- digestive track and body wall
- Body cavity called
coelom
- cushions organs
- fluid resistance for muscles
- allows organs to move independently
- Not all triploblasts have a coelom

Mammals develop subdivided body cavities from coelom

- The dorsal cavity and the ventral cavity are the largest body compartments.
- Dorsal body cavity includes the cranial cavity, enclosed by the skull, and the spinal cavity, enclosed by the spine
- Ventral body cavity subdivided into 2 compartments
- thoracic contains the lungs and heart
- abdominopelvic contains the kidneys, ureters, stomach, intestines, liver, gallbladder, pancreas, bladder, anus and reproductive system
Evolution of animal size and shape
- Animal body plans are expressions of the genome, but the product of millions of years of evolution
- Animals body plans are constrained by physical laws
- diffusion, size and movement, heat exchange
- gravity (land), pressure (aquatic)
- Example: Properties of water and animal shape
- water more dense than air = surface bumps cause drag
- natural selection favored tapered smooth bodies
- convergent selection across aquatic vertebrates

Form and function in biology

Example: Diversity of bird form

Movie monsters are mostly not possible…. Godzilla
- At that size, Godzilla’s heart wouldn’t be able to pump blood to the brain.
- Brain would send messages too slowly to muscles, so wouldn’t be able to move properly
- Godzilla would have to sunbathing constantly to stay warm

Exchange with environment limits animal bodies
- Animals must uptake nutrients, expel waste and exchange gases
- occurs across plasma membrane of cells
- Simple internal body plan: Cnidaria (jellyfish)
- outer tissues exposed to environment
- gastrovascular cavity also open to environment

Exchange with environment limits animal bodies
- Animals must uptake nutrients, expel waste and exchange gases
- occurs across plasma membrane of cells
- Body plan optimized for surface area: Flatworms
- thin, flat shape
- lots of outer cells exposed to environment

Exchange with environment limits animal bodies
- Animals must uptake nutrients, expel waste and exchange gases
- occurs across plasma membrane of cells
- Many animals (like humans) have more complex internal bodies
- reduces total # of cells on outer surface
- volume > surface area
- ‘think’ whale versus flea
- Internal structures for exchange evolve…
- highly branched or folded
- e.g., lungs, intestines, kidneys

Exchange with environment limits animal bodies
- Animals must uptake nutrients, lose waste and exchange gases
- occurs across plasma membrane of cells
- Many animals (like humans) have more complex internal bodies
- reduces total # of cells on outer surface
- ‘think’ whale versus flea
- Internal organs for exchange evolve…
- highly branched or folded
- digestion, respiration and circulation
- fluids connect structures to other cells

What are the advantages of a complex body plan?

- Sensory organs (eyes, ears, etc.)?
- Internal digestion organs?
- Specialized filtration systems?
- How do internal systems allow life on land?
Hierarchy of animal body plans
- Cells with similar function grouped into tissues
- Different tissues organized into functional units: Organs
- Groups of organs can work together: Organ systems
- There are a limited set of tissues in animals
- epithelial:
- connective:
- muscle:
- nervous:

